The present invention relates to devices that are retained inside a body passage and in one particular application to vascular stents for the repair of arterial dilations known as aneurysms.
As a result of arteriosclerosis, portions of blood vessels may become weakened and extremely dilated. These dilated vessels may be treated by bridging the dilation or weakened extended area using a vascular tubular prosthesis. In this way the diseased portion of the vessel is effectively isolated from the pressure inside blood vessels.
Vascular tubular prostheses may be inserted into the diseased portion of the vessel by surgically opening the vessel and suturing the prosthesis into position. However, it may be preferred to insert the prosthesis from a remote opening, such as the femoral artery, adjacent the groin, using a catheter system. This is because the elimination of the need to open a major body cavity may diminish the potential surgical complications.
Generally it is desirable to insert the prosthesis, using a catheter, in a collapsed or compressed condition and then to expand the prosthesis when in position. One reason for this is that it is desirable to avoid substantially occluding the blood flow during the insertion process. Therefore, by collapsing the prosthesis, the prosthesis may be readily positioned inside the vessel, in some cases without substantially occluding the blood flow.
There are generally two techniques for expanding the prosthesis once in position at the location to be repaired. One technique uses a malleable metal prosthesis which has two configurations. One configuration has a relatively smaller diameter and the other has a relatively radially expanded configuration contacting and securing to a neck portion on either side of the diseased vessel region. The prosthesis may be a malleable metal ring which may be expanded by a balloon catheter to set the prosthesis in its expanded diameter, inside the neck portion, proximate to the diseased portion of the vessel.
Another general approach is to use a self-expandable prosthesis which may be compressed against a resilient bias. Once in position, the prosthesis is allowed to resiliently expand into contact with the vessel wall.
While a wide variety of solutions have been proposed to the problem of effectively bypassing diseased tissue, various existing prosthetic device designs may have certain deficiencies. For example, in some cases, the neck portion on either side of the diseased vessel portion may be relatively short. This makes it difficult for prosthetic devices to adequately engage the narrow neck on either side of the aneurysm.
In addition, some of the existing prostheses may cause blockage of the blood flow during insertion of the prosthesis, which can have physiologically adverse affects. Still another issue is that many existing prostheses do not adequately seal against the internal surface of a vessel, allowing leakage of blood past the prosthesis into the region between the prosthesis and the weakened blood vessel. The consequences of this type of leakage can be traumatic. In some designs, the device may not be adaptable to non-circular or irregularly shaped neck regions.
Still another issue with some known prostheses is that they may require the hospital to stock a variety of prosthesis sizes for different situations and different patient physiologies. Also some designs may require that the prosthesis be custom fitted for each particular patient.
Another difficulty may arise with regard to accurately positioning the prosthesis once it has been expanded. In some cases inaccurate positioning may be problematic. Similarly, in many existing prostheses it is possible that the prosthesis may be dislodged from its desired position so that it does not effectively accomplish its function of protecting the weakened vessel.
Thus, for these and other reasons, there is a continuing need for enhanced solutions to the problem of repairing diseased vessels and in general to the problem of effectively securing prosthetic devices to the internal walls of body passages.
According to one aspect of the present invention, a device for retaining a prosthesis in a body passage includes an annular, resilient element. The element has an undeformed diameter greater than the diameter of the body passage.
According to another aspect of the present invention, a prosthesis for insertion into a body passage includes an annular, resilient spring element and a tubular graft. The graft may be attached to the element. The element has an undeformed diameter greater than the diameter of the graft.
According to still another aspect of the present invention, a vascular prosthesis for repairing a diseased first vessel includes a resilient, annular ring having a first pair of loops extending in one direction, and a second pair of loops, extending in the opposite direction. The first and second pairs of loops are connected together. A tubular graft is connected to the ring. The graft is arranged to extend along the length of the first vessel and the first pair of loops are arranged to extend at least partially past the point where a second vessel intersects the first vessel. One of the second pair of loops defines an opening to permit communication between the first and second vessels, at least partially past the prosthesis.
According to yet another aspect of the present invention, a method of securing a prosthetic device in a body passage includes the step of folding a resilient annular ring to assume a first configuration having a cross-sectional area smaller than the cross-sectional area of the undeformed ring. The ring is positioned at a desired location within a body passage and allowed to resiliently deform to a second configuration, having a larger diameter then the first configuration, but still having a cross-sectional area smaller then that of the undeformed ring.
According to but another aspect of the present invention, a method for repairing a diseased vessel includes the step of folding an annular ring on its diametric axis to assume a smaller cross-sectional configuration and forming a pair of loops extending away from the axis. The ring is arranged in the vessel with its diametric axis proximate to an intersecting vessel such that the loops extend at least partially past the intersecting vessel without occluding the intersecting vessel.
According to yet another aspect of the present invention, a method for securing a prosthetic device inside a body passage includes the step of deforming an annular resilient spring by folding said spring along its diametric axis. The spring is positioned inside a body passage. The spring expands resiliently against the body passage. The spring continuously presses outwardly against the body passage.
According to but another aspect of the present invention, a prosthetic device includes a prosthetic heart valve, a flexible tubular sleeve having a first end connectable to the valve and a second end. A deformable, resilient annular ring is connected to the second end and arranged to connect the graft to the interior surface of a portion of the ascending aorta.
According to yet another aspect of the present invention, a prosthesis for insertion into a body passage includes at least two annular resilient spring elements and a flexible, tubular graft attached to each of the elements. A rigid member longitudinally connects the elements. The rigid member is less flexible than the graft.